Investigations of 1-(N-substituted carbamoyl)-5-fluorouracil derivatives have been made, because there are many carcinostatically active compounds among them. 1-[N-(monoalkyl substituted cyclohexyl) carbamoyl]-5-fluorouracil, 1-[N-(dialkyl substituted cyclohexyl) carbamoyl]-5-fluorouracil, 1-[N-(monomethoxy substituted cyclohexyl) carbamoyl]-5-fluorouracil and others were indicated in Japanese Patent Application Disclosure No. 56678/'78, 1-[N-(cyclohexylmethyl) carbamoyl]-5-fluorouracil, 1-[N-(methyl substituted cyclohexylmethyl) carbamoyl]-5-fluorouracil, 1-[N-(p-methoxy substituted cyclohexylmethyl) carbamoyl]-5-fluorouracil and others were indicated in Japanese Patent Application Disclosure No. 56679/'78, 1-(N-benzyl carbamoyl)-5-fluorouracil, 1-[N-(p-fluoro substituted benzyl) carbamoyl]-5-fluorouracil, 1-[N-(p-methoxy substituted benzyl) carbamoyl]-5-fluorouracil, 1-(N-phenetyl-carbamoyl)-5-fluorouracil and others were indicated in Japanese Patent Application Disclosure No. 59680/'78, 1-[N-(1-methyl-3-phenylpropyl) carbamoyl]-5-fluorouracil, 1-[N-(3-phenylpropyl) carbamoyl]-5-fluorouracil, 1-[N-{2-(4-methylphenyl) propyl} carbamoyl]-5-fluorouracil and others were indicated in Japanese Patent Application Disclosure No. 136267/'80, and various 1-(N-heterocyclic group substituted carbamoyl)-5-fluorouracil and the derivatives of them, 1-[N-heterocyclic group substituted alkyl) carbamoyl]-5-fluorouracil and the derivatives of them were indicated in Japanese Patent Application Disclosure No. 63966/'81. Among these known 1-(N-carbamoyl)-5-fluorouracil derivatives, 1-(N-hexyl-carbamoyl)-5-fluorouracil has been put to practical use, but investigations of the others are still insufficient.